We studied 39 cases with one of these three conditions for FGFR2 exon 111a or exon 111c previously reported only in Crouzon syndrome are present also in one of the other two syndromes. Two insertions, one in exon 111a in a Crouzon syndrome patient and the other in exon 111c in a Pfeiffer syndrome patient, were observed. The latter mutation has the same alternative RNA splicing effect as a reported synonymous mutation for Crouzon syndrome. A missense mutation, V359F, was detected in a family with one member with craniosynostosis and broad digits, diagnostic of Pfeiffer syndrome, and with two members with features consistent with Crouzon syndrome, craniosynostosis without limb anomalies. The inter-and intrafamilial variability in expression of FGFR2 mutations suggests that these three syndromes, presumed to be clinically distinct, are instead representative of a spectrum of related craniosynostotic and digital disorders.